1. Field
Example embodiments relate to wire grid polarizers, methods of fabricating a wire grid polarizer, and display panels including a wire grid polarizer. Other example embodiments relate to a method of fabricating a wire grid polarizer by which a large-size wire grid polarizer is easily fabricated, a wire grid polarizer fabricated by the above method, and a display panel including a wire grid polarizer.
2. Description of the Related Art
Image forming apparatuses (e.g., liquid crystal display devices), which require a separate light source, use a polarizer as an element for forming an image by controlling transmission/shutting of light. However, because an absorption-type polarizer has been mainly used as a polarizer, only half of light emitted from a light source is used and the remaining half of the light is absorbed by the polarizer. The absorption-type polarizer is considered to be one of the major contributors to the reduction in the light-use efficiency of a display device. For example, in a liquid crystal display device, because a polarizer is arranged on each of front and rear surfaces of a liquid crystal layer, the light-use efficiency is only below 10% including light loss due to a color filter. This means that only about 10% of the light emitted from a backlight unit actually contributes formation of an image.
Such a low efficiency is a problem in power consumption of high bright electronics (e.g., televisions (TVs)). Accordingly, a variety of methods have been suggested to address the low light-use efficiency. For example, there is a method of attaching a bright enhancement film such as a dual brightness enhancement film (DBEF) to a backlight unit. However, the additional use of an optical film raises costs.
Recently, a reflection-type polarizer (e.g., a wire grid polarizer) is used instead of the absorption-type polarizer. A wire grid polarizer is a polarizer in which a plurality of conductive nano wires are arranged parallel to each other on a transparent insulation substrate. In general, when a pitch of the parallel-arranged nano wires is close to or greater than the wavelength of incident light, a typical diffraction phenomenon occurs. However, when a pitch of the nano wires is smaller than the wavelength of incident light, a polarization separation phenomenon occurs much more than diffraction. For example, when a pitch of nano wires is not greater than about 100 nm, light that is polarized in a direction parallel to the nano wires is reflected, whereas light that is polarized in a direction perpendicular to the nano wires is transmitted. Thus, only a light component in a particular polarization direction perpendicular to the nano wires may be transmitted to the wire grid polarizer. Because the other light component is reflected without being absorbed, most of the incident light may be substantially used by changing the polarization direction of the reflected light.
As described above, to allow the wire grid polarizer to appropriately function as a polarizer throughout the entire range of visible ray, the pitch of nano wires needs to be at least 100 nm or smaller. Also, as an aspect ratio of nano wires increases (i.e., the height of nano wires is greater than the width thereof), a polarization separation ratio of a wire grid polarizer is improved. Nevertheless, it is very difficult to fabricate a large-size wire grid polarizer satisfying the above conditions. Despite the many merits described above, the wire grid polarizer has not been widely used for large-size display devices (e.g., TVs).